Like Tourist I believe the reaction to Shoreham is over the top. There is as much risk of A380 bits falling into farnborough after an accident as the red Arrows doing a flypast.ie almost nil.
Also how do we know that debris will fall in the sterile area. There is no possibility of an airliner displaying at farnborough staying within the airfield boundary or avoiding built up areas.
The level of risk of a one off vintage jet accident, which randomly happened to fall onto a road rather than the many open areas around, does not pose such a risk as to decimate the UK display scene for ever.